Contemporary communication systems may employ wireless and/or wireline transmission technologies for conveying data from a source to a destination. Users typically employ different specialized devices for accessing particular types of communication services, such as voice, data, and/or messaging services. For example, a cellular telephone may be used to make a wireless voice call, a wireless personal digital assistant (PDA) may be used to send and receive e-mail messages, a facsimile machine may be used for facsimile transmissions using a plain old telephone system (POTS) landline, and/or a desktop computer may access multimedia applications using digital subscriber line (DSL) over shielded twisted pair. As a result, these transmission-specific or network-specific devices may dictate that users be required to have numerous devices to perform a range of desired communication functions. The need for multiple devices may add complexity to the provisioning of robust communication solutions.
Further complicating communication solutions is the fact that each device may require a unique service agreement, or subscription, with a service provider. For example, a user may have a service contract with a wireless carrier for cellular phone service, a service agreement with a separate provider for DSL service and still another service agreement for conventional landline telephone service. The need to have a unique identifier for each device used by a user may add further complexity to contemporary communication solutions. Each service provider may require that a user have a unique identifier associated with its network. For example, a user may have one number assigned to them for a cellular phone account, a separate number assigned for a landline account, and an e-mail address, or Ethernet address, assigned for a DSL account. As a result, the user needs to keep track of these identifiers and may have to ensure that other parties have these identifiers in order to communicate with the user.
It is generally desirable to enable communications among parties via whatever means or modes of communication are available to them. For example, a cellular or wireless user can readily exchange phone calls with PSTN users. However, technologies have yet to be ubiquitously deployed wherein a telephone caller may readily communicate with an instant messaging client on a personal computer for example. Aside from a desire to support cross-communications of this type, it is desirable for a user to freely employ any mode of communication available, even using diverse modes of communication from the same device. Accordingly, some devices recently developed may support multiple modes of communication. For example, an otherwise conventional mobile telephone device communicating via 2G or 3G may also be equipped to recognize a nearby WiFi ‘hot spot’ and establish communications through the latter.
In the context of multimodal communications devices, such as wireless communication devices that can support more than one wireless protocol or carrier frequency band, several modes of communication may sometimes be available. At any given time and place one type of communication may be preferred over others due to proximity, low cost, better quality or higher reliability. However, the choice of a mode of communication is controlled by a network, and may occur at any time either upon initiation of a session or during a session. A so-called ‘mid-call hand-off’, wherein the mode of access changes while a session is maintained, may take place without warning and may cause a brief interruption in the communications between parties.
Furthermore, the change from one mode to another, initiated by a network-resident entity, may result in a suddenly changing the connection to one that is less desirable to the user. For example, a connection with a superior signal strength may exhibit lower bandwidth, lesser security or greater cost. The mid-session switching of access modes may occur without regard to the user's desires or preferences, resulting in undesirable operation.